1. Field of the Invention
The present invention relates to the field of wireless networks.
2. Discussion of Related Art
It is well known that a number of networks and service providers can exist simultaneously within a particular geographical area. With this environment in mind, establishment of communication between a mobile device within the geographical area and another communication device often involves the handoff of the signal from one network to another network as the person operating the mobile device moves within the geographical area. Since there often are many variations in access networks, service providers and mobile devices, it is very difficult to assure seamless communication within the geographical area for a variety of mobile devices.
One proposal at establishing seamless communication for mobile users as well as application service providers is to use a Hyper Operator Overlay architecture, such as described in F. Watanabe, J. Cao, S. Kurakake, “Geographical access network topology estimation in heterogeneous access networks,” IEEE VTC'02 paper no. 775.
An example of a known Hyper Operator Overlay network architecture is schematically shown in FIG. 1. The Hyper Operator Overlay (HOO) network architecture 100 combines different access networks to provide the most suitable access network to each available service. The HOO network 100 includes different access networks 102A-D, service/content providers 104A-B and a hyper operator 106 located in the Internet. Nodes 112A-D of the access networks 102A-D are in communication with Hyper Operator Overlay nodes 114A-B of the Internet which are in turn in communication with a Hyper Operator Overlay node 114C Thus, nodes 112A-D are in communication with Hyper Operator Overlay node 114C. The hyper operator 106 communicates with the Hyper Operator Overlay nodes 114A-C, access networks 102A-D, service providers 104A-B and company intranet 108 and works to coordinate different access networks and service providers 104A-B (such as, yahoo.com) including private intranets (e.g. company intranet 108) in order to have seamless communications.
The mobile device, such as a cell phone, PDA or a lap top computer 110, supports different access network technologies such as WLAN, mobile phone, Bluetooth, ADSL, etc. Instead of having several service agreements with different access networks 102 and service providers 104, a user using the mobile device will only need to have a single service agreement with the hyper operator 106. Because of a service contract with the hyper operator 106, the user can gain access to different access networks 102 by the mobile device without establishing new service contracts.
The HOO network 100 does not require modifications to existing access networks. The HOO network 100 can work as a broker or a bridge between different access networks and service providers, and can coordinate service offered by different access networks and service providers. As described in S. Weinstein, “The mobile internet: wireless LAN vs. 3G cellular mobile,” IEEE Commun. Mag., vol. 40 no. 2, pp. 26-28, February 2002, the HOO network 100 has three features of interest:
1) For end users who are already subscribers of major service providers, transparent Internet access is provided in many local environments without having to subscribe with each Palm LAN operator
2) For major service providers, extension of services offered to their subscribers without having to invest in additional access infrastructure; and
3) For public access wireless LAN operators, a vast potential user population acquired without having to sign up individual customers.
In the hierarchical coverage area of the HOO network 100, there may be a variety of sizes of access networks, as described in E. A. Brewer et al., “A network architecture for heterogeneous mobile computing,” IEEE Pers. Commun., vol. 5, no. 5, pp. 8-24, October 1998 and M. Stemm and R. H. Katz, “Vertical handoffs in wireless overlay networks,” Mobile Networks and Applications, vol. 3, no. 3, pp. 335-350, 1998. An access network with small coverage area has a relatively high-bandwidth, while an access network with large coverage area has a relatively small bandwidth. The vertical handoff between different access networks can be classified into two categories: an upward vertical handoff is a handoff to a wireless overlay with a larger cell size (and lower-bandwidth) and a downward vertical handoff is a handoff to a wireless overlay with a smaller cell size (and higher bandwidth). It is well known that the upward vertical handoff has a time critical issue of handoff processing time when the mobile device moves out from the access network with a smaller cell to that with a larger cell. Also, a quick authentication and QoS adjustment are required, especially for real time applications such as video and voice, because different access networks possess inherent diversity in terms of operating frequencies, access schemes, QoS supports, monetary costs, and traffic conditions.
However, current independent management for user, mobility, resource allocation, authentication/authorization, security at each access network makes it difficult to coordinate heterogeneity and to maintain connectivity. In addition, minimizing modification of the current access network would be preferable. A couple of schemes to coordinate network heterogeneity and to maintain connectivity have been considered. One approach proposes a common core network to coordinate various access networks as described in G. Wu, “MIRAI architecture for heterogeneous network,” IEEE Commun. Mag., vol. 40, no. 2, pp. 126-134, February 2002. This approach attempts to construct the common core network between the Internet and access networks to handle heterogeneity of different access networks. It requires additional modification to converge different network cores whose functions are mobility management, authentication/authorization, paging etc. Therefore, existing access network operators may not be able to join the new common core network architecture easily. In addition, the infrastructure installation cost is expected to increase. Also, the common core network does not absorb heterogeneity of higher layer requirements.
Another approach for coordinating heterogeneity and maintaining connectivity is to use the cooperative and enhanced hybrid networks (DRiVE project) which interface directly with access networks and the Internet as described in R. Walsh, L. Xu, T. Paila, “Hybrid networks—as step beyond 3G,” WPMC'00 pp. 109-114, Bangkok, November 2000.
In order to realize both of the above described approaches for mitigating heterogeneity, the new core, which integrates an independent management owned by each access network, has to be developed and installed. Furthermore, the need for a standardization effort and business commitment is inevitable.
The geographical access network configuration (e.g., location of base station, coverage area, capacity etc) is assumed to be known to the operator because the operator owns its access network. However, the Hyper Operator will not own the access network. It only owns users. Whenever the user uses an access network, the access network operator will charge to the Hyper Operator. In this model, the Hyper Operator may not be able to get geographical access network information easily. Even if the Hyper Operator can get this information, the geographical coverage area, especially WLAN and WPAN (wireless personal area network, like Bluetooth), is dynamically changed. Therefore, the latest geographical access network information is not available in the Hyper Operator.